DescriptionMales measure 32.99-34.8 mm in SVL and the single female specimen measured 41.04 mm in SVL. Head is flat dorsally. Snout is short; in dorsal view it is acute and in profile it projects. Canthus rostralis is well-defined. External nostrils are very slightly prominent; they are lateral, oval, postero-laterally directed, and located closer to the tip of the snout than to the eyes. Inter-narial region is slightly concave. Loreal region is concave. Tympanum, tympanic ring, and columella auris pharyngea ostia are all absent. Prominent supratympanic fold is present. Choanae are oval and small. Spatulate tongue without apparent notch, free in the posterior third. Parotoid glands are only slightly evident. Forearms are robust. Fingers have rounded tips. Hands have vestigial webbing. Palmar surfaces with abundant low tubercles. Hind limbs are short. Knees, ankles and tarsus are without folds. Feet are moderately webbed,with fingers I, II, and V fully webbed, III with 1 ½ phalanges free and IV with 2 ½ phalanges free. The outer metatarsal tubercle is rounded and raised while the internal metatarsal tubercle is flat and round. Small and irregular low tubercles are abundant on the plantar surface. Head and trunk are thick and smooth with some warts on trunk. Forelegs and hind legs are covered with small warts, ventral surfaces are granular. Large warts on flank.
Males have paired vocal slits and have more robust forearms than females.
Males also have rather bulky nuptial excrescences on the pollices, consisting of a patch of keratinized fine spinules covering the dorsal surface of finger I (Ardila-Robayo and Ruiz-Carranza 1998).

In life, the dorsum is pea green with scattered black spots, freckles and/or black. Flanks are cream and black (in Colombian specimens) or yellowish-cream with a thick black reticulation (in Ecuadorian females). The venter is creamy white with small black spots that are elongated in shape and irregular size, and may be individual or coalescent (in Colombian specimens), or orange and black (in Ecuadorian specimens). Palms and soles are yellow. Iris greenish yellow with thick black circular line, parallel to the pupil (in Colombian specimens), or dark brown with yellow edging on the pupil (in Ecuadorian specimens) (Ardila-Robayo and Ruiz-Carranza 1998; Coloma et al. 2010).

Atelopus angelito is known only from two localities, one in southern Colombia (the type locality) and the other in northern Ecuador. In Colombia it is found in Parque Nacional Natural Puracé (in the subpáramo of Páramo de las Papas), Departamento del Cauca on the eastern slopes of the Cordillera Central (Ardila-Robayo and Ruiz-Carranza 1998). In Ecuador it occurs in Reserva Ecológica El Ángel (at Río La Plata, Comunidad de Morán), Provincia Carchi on the western slopes of the Cordillera Occidental (Yánez-Muñoz and Altamirano B. 2005; Coloma et al. 2010). Only found in páramo and subpáramo habitats at elevations of 2500-3000 m. At the Ecuadorian locality, which is 14 km southeast of Maldonado, average annual rainfall is 1,051 mm, and the average annual temperature is 14.2°C (Coloma et al. 2010).

Life History, Abundance, Activity, and Special BehaviorsThis very rare species is found on vegetation along side streams in montane Andean forests and sub-páramo bush land. One of the two Ecuadorian female specimens was found under a stone. There is no information known about breeding habitats, or its ability to tolerate habitat disturbance (Stuart et al. 2008). The Colombian specimens were collected during the day, on the ground near a populated area (Ardila-Robayo and Ruiz-Carranza 1998).

Trends and ThreatsThis species has been characterized as Critically Endangered, and Possibly Extinct until surveys confirm otherwise. The population has suffered dramatic declines, decreasing more than 80% in the last two decades. Although Stuart et al. (2008) mentioned that this species was collected in Colombia as recently as 2000, no source was cited; no other published reports have been made since it was last collected on 12 April 1995 in Colombia (Ardila-Robayo 2005). There have apparently not been any additional surveys for it (Coloma et al. 2010). In Ecuador the only two specimens were collected on 22 July 1988, and numerous additional surveys since then have not found this species (Coloma et al. 2010).

There have been serious declines of other high-elevation Atelopus species in the region, mainly due to chytridiomycosis and suggesting that this species might also be at risk (Coloma et al. 2010). Amphibian chytrid fungus was found in 1993 at an Ecuadorian locality (42 km west of Tulcán, Provincia Carchi) near that of Atelopus angelito (Merino-Viteri 2001; Coloma et al. 2010).

The type locality is within Parque Nacional Natural Puracé, Colombia but additional protection from habitat disturbance might be beneficial (Stuart et al. 2008). In Ecuador it occurs within a protected area, Reserva Ecológica El Ángel, Provincia Carchi (Yánez-Muñoz and Altamirano B. 2005). More research into this species' population status and ecological requirements is needed (Stuart et al. 2008).

CommentsDescribed by Ardila-Robayo and Ruiz-Carranza (1998).

The genus Atelopus, with 113 described and putative species, appears to be the most threatened clade of amphibians (La Marca et al. 2005). Chytridiomycosis is thought to be a primary factor in the decline and disappearance of species in this genus (La Marca et al. 2005). At least 30 Atelopus species appear to be extinct, having been missing from all known localities for at least 8 years (La Marca et al. 2005). Only 52 of the surviving species have sufficient data with which to evaluate population trends; of these, 81% (42 of 52) have population sizes that have been reduced by at least half (La Marca et al. 2005). Higher-elevation species (those living at least 1000 m asl) have been hit the worst, with 75% (21 of 28) having disappeared entirely (La Marca et al. 2005). Most Atelopus species are local endemics and are restricted to very limited areas along mid- to high-elevation streams (generally 1500-3000 m asl, though the maximum vertical range is from sea level to permanent snow; Lötters 2007), a habitat preference frequently associated with the co-occurrence of chytridiomycosis (La Marca et al. 2005). At least 26 species are known only from a single population inhabiting a narrow altitudinal range (La Marca et al. 2005). Due to their restricted ranges, they are thought to have limited ability to adapt to warming climatic conditions (Lötters 2007).